The present invention relates generally to medical devices and particularly to a balloon catheter with dilation elements along the exterior surface of the balloon.
Balloon catheters are widely used in the medical profession for various intraluminal procedures. One common procedure involving the use of a balloon catheter relates to angioplasty dilation of coronary or other arteries suffering from stenosis (i.e., a narrowing of the arterial lumen that restricts blood flow).
Although balloon catheters are used in many other procedures as well, vascular angioplasty using a balloon catheter has drawn particular attention from the medical community because of the growing number of people suffering from vascular problems associated with arterial stenosis. This has lead to an increased demand for medical procedures to treat such problems. The widespread frequency of vascular problems may be due to a number of societal changes, including the tendency of people to exercise less while eating greater quantities of unhealthy foods, in conjunction with the fact that people generally now have longer life spans than previous generations. Angioplasty procedures have become a popular alternative for treating arterial stenosis because angioplasty procedures are considerably less invasive than other alternatives. As an example, stenosis of the coronary arteries has traditionally been treated with bypass surgery. In general, bypass surgery involves splitting the chest bone to open the chest cavity and grafting a replacement vessel onto the heart to bypass the blocked, or stenosed, artery. However, coronary bypass surgery is a very invasive procedure that is risky and requires a long recovery time for the patient.
To address the increased need for vascular treatments, the medical community has turned to angioplasty procedures, in combination with stenting and other procedures, to avoid the problems associated with traditional open surgery. Typically, angioplasty procedures are performed using a balloon-tipped catheter that may or may not have a stent mounted on the balloon (also referred to as a stented catheter). The physician performs the angioplasty procedure by introducing the balloon catheter into a peripheral artery (commonly one of the leg arteries) and threading the catheter to the narrowed part of the artery to be treated. During this stage, the balloon is uninflated and collapsed onto the shaft of the catheter in order to present a low profile which may be passed through the vasculature. Once the balloon is positioned at the narrowed part of the artery, the balloon is expanded by pumping a mixture of saline and contrast solution through the catheter to the balloon. As a result, the balloon presses against the inner wall of the artery to dilate it. If a stent is mounted on the balloon, the balloon inflation also serves to expand the stent and implant it within the artery. After the artery is dilated, the balloon is deflated so that it once again collapses onto the shaft of the catheter. The balloon-tipped catheter is then retracted from the body. If a stent is mounted on the balloon of the catheter, the stent is left permanently implanted in its expanded state at the desired location in the artery to provide a support structure that prevents the artery from collapsing back to its pre-dilated condition. On the other hand, if the balloon catheter is not adapted for delivery of a stent, either a balloon-expandable stent or a self-expandable stent may be implanted in the dilated region in a follow-up procedure. Although the treatment of stenosed arteries is one common example where balloon catheters have been used, this is only one example of how balloon catheters may be used and many other uses are also possible.
One problem that may be encountered with conventional angioplasty techniques is the proper dilation of stenosed regions that are hardened and/or have become calcified. Stenosed regions may become hardened for a variety of reasons, such as the buildup of atherosclerotic plaque or other substances. Hardened regions of stenosis can be difficult to completely dilate using conventional balloons because hardened regions tend to resist the expansion pressures applied by conventional balloon catheters. One solution that has been offered for dilating hardened stenoses is special balloon catheters with dilation wires or beads that extend along the length of the balloon. The dilation wires and/or beads focus that dilation pressure of the balloon onto the narrower contact area between the dilation wire or bead and the vessel wall. As a result, the increased, focused pressure may crack and/or break up the hardened stenosis, thereby allowing the vessel lumen to be expanded.
Many balloon catheters with dilation wires or beads are manufactured by attaching a separate wire or other material to the exterior of the balloon. This may be accomplished, for example, by using adhesives to bond the dilation element to the balloon. This approach has several advantages, including being able to use an optimized material and shape for the dilation element and manufacturing processes that are relatively straightforward. However, separate dilation elements can be disadvantageous because there may be concern by physicians that the dilation element could break loose from the surface of the balloon. Thus, dilation elements that are integral with the balloon may be preferable despite some of the advantages of separate dilation elements.
Another concern with balloons that have dilation elements along the exterior of the balloon is that the dilation elements tend to make the balloon less flexible. Flexibility is particularly important for balloon catheters because they are frequently used to traverse narrow passageways with tortuous paths. Accordingly, the inventor believes it would be desirable to provide a balloon catheter with integral dilation elements that are flexible.